The effect of intermittent versus chronic energy restriction on breast cancer risk biomarkers in premenopausal women: a randomised pilot trial

Background

Postmenopausal breast cancer risk increases twofold in women who gain significant amounts of weight [1] and there is evidence that energy restriction may reduce risk [2]. Animal studies indicate that intermittent energy restriction (IER) reduces risk and may be superior to continuous energy restriction (CER) [3]. We have shown that CER reduces breast cancer risk biomarkers in women but is hard to maintain. We hypothesise that IER may be superior to CER in reducing biomarkers of breast cancer risk and may also be more acceptable to women.

Methods

One hundred and eight premenopausal women, mean age 40.0 years (SD = 4.0), mean adult weight gain 20.1 kg (SD = 11.0), were randomised to either CER (75% estimated energy requirements: ~1,500 kcal 7 days/week) or IER (75% estimated energy requirements: 650 kcal for 2 days and ~1,800 kcal 5 days/week) over 6 months. The study endpoints are weight and body composition (waist/hip circumference, fat free and total fat mass by bioelectrical impedence), measures of insulin sensitivity (HOMA, SHBG, testosterone), potential breast cancer growth factors (IGF axis, leptin adiponectin), inflammatory markers (C-reactive protein and sialic acid) and oxidative stress markers (serum isoprostane). The relative acceptability of IER and CER will be assessed using a quality of life questionnaire (RAND SF-36) and scales of behaviour change and adherence.

Results

Nineteen participants (17.6%) have withdrawn from the study (IER = 12, CER = 7; main reasons: stress = 4, pregnancy = 3, change in employment = 3, could not stick to diet = 3). Baseline to 6-month results for weight and body composition are reported in Table 1.

Table 1 Six-month results

Conclusion

Significant decreases in weight, fat and waist occurred in both groups over 6 months, with the IER group doing slightly better. Greater proportions of the IER group achieved 5% weight loss (IER 79% cf. CER 66%, P = 0.19) and 10% weight loss (IER 43% cf. CER 28%, P = 0.13). We await results for biochemistry and relative acceptability, which will be presented at the meeting.